If its not all eaten within 24 hours I would replace it with a fresh batch.
Were you planning on going away on holiday or something?
Being a seaweed agar and not the cow gelatin I would imagine it could last quite a while.
I think what I used was vegetable agar. The longest record, so far, was 16 hours staying in the tank and not any strange odor.( of course being taken out from the tank, break it and smell......)
I will try keeping them in the tank longer and see what happened.